let num1: number = 123;
let str: string = "nj";
let bool: boolean = false;
let arr: string[] = ["kkk"]; // 数组的存放类型是单一的

let info = {
  username: "wxj",
  age: 18,
};

let isnull = null;
let isundefined = undefined;

// 通常不加返回类型
const add = (num1: number, num2: number): string => {
  return num1 + num2 + "";
};

const add1 = (option: { username: string; age: number,sex?:string }) => {
  console.log(option);
};

add1({
  username: "123",
  age: 18,
});

export {};
